ABSTRACT: The objectives of the proposed research concerning bioactivation and detoxification of toxic materials are enumerated below: (1) Purification of rat liver microsomal cytochromes P-450 to homogeneity. (2) Purification of rabbit lung microsomal cytochrome P-450 and NADPH-cytochrome P-450 reductase to homogeneity. (3) Physical characterization of the above purified enzymes and comparison of these cytochromes P-450 with each other (and with rabbit liver microsomal cytochromes P-450) with regard to physical properties and substrate specificities towards toxic compounds of environmental interest. (4) Understanding the activities of the various cytochromes P-450 as concerns the substrate specificity towards N-nitrosamines, particularly dimethylnitrosamine. (5) Elucidation of the role (and modes) of covalent binding in the toxicity of pyrrolizidine alkaloids. (6) Elucidation of the modes and roles of metabolic activation and covalent binding of a model furan compound in the toxicity, mutagenesis, and possibly malignant transformation observed with that compound. (7) Understanding the interaction between rat liver microsomal cytochromes P-450 and NADPH-cytochrome P-450 reductase. (8) Development of immobilized enzyme technology for the reconstituted mixed function oxidase systems. (9) Elucidation of the mechanism of destruction of free and cytochrome P-450-bound heme by NADPH-cytochrome P-450 reductase (in the absence of unsaturated lipids).